Find a sublist of anagrams, for a word, in a list of words

anagram.exs

defmodule Anagram do
    def match(word,words) do
      Enum.filter(words, fn(w) ->
        source = String.downcase(word)
        compare = String.downcase(w)
        if source === compare do
          false
        else
          a = to_char_list(source) |> Enum.sort
          b = to_char_list(compare) |> Enum.sort
          a == b
        end
      end)
    end
end

ExUnit.start

defmodule AnagramTest do
  use ExUnit.Case, async: true

   test "no matches" do
      matches = Anagram.match "diaper", ["hello", "world", "zombies", "pants"]
      assert matches == []
    end

    test "detect simple anagram" do
      matches = Anagram.match "ant", ["tan", "stand", "at"]
      assert matches == ["tan"]
    end

    test "detect multiple anagrams" do
      matches = Anagram.match "master", ["stream", "pigeon", "maters"]
      assert matches == ["stream", "maters"]
    end

    test "do not detect anagram subsets" do
      matches = Anagram.match "good", ~w(dog goody)
      assert matches == []
    end

    test "detect anagram" do
      matches = Anagram.match "listen", ~w(enlists google inlets banana)
      assert matches == ["inlets"]
    end

    test "multiple anagrams" do
      matches = Anagram.match "allergy", ~w(gallery ballerina regally clergy largely leading)
      assert matches == ["gallery", "regally", "largely"]
    end

    test "anagrams must use all letters exactly once" do
      matches = Anagram.match "patter", ["tapper"]
      assert matches == []
    end

    test "detect anagrams with case-insensitive subject" do
      matches = Anagram.match "Orchestra", ~w(cashregister carthorse radishes)
      assert matches == ["carthorse"]
    end

    test "detect anagrams with case-insensitive candidate" do
      matches = Anagram.match "orchestra", ~w(cashregister Carthorse radishes)
      assert matches == ["Carthorse"]
    end

    test "anagrams must not be the source word" do
      matches = Anagram.match "corn", ["corn", "dark", "Corn", "rank", "CORN", "cron", "park"]
      assert matches == ["cron"]
    end

    test "do not detect words based on checksum" do
      matches = Anagram.match "mass", ["last"]
      assert matches == []
    end

end